Showerhead electrodes

ABSTRACT

A silicon-based showerhead electrode is provided that can include a backside, a frontside, and a plurality of showerhead passages extending from the backside of the silicon-based showerhead electrode to the frontside of the silicon-based showerhead electrode. The silicon-based showerhead electrode can comprise single crystal silicon. The silicon-based showerhead electrode may further include a plurality of partial recesses formed within the single crystal silicon along the backside of the silicon-based showerhead electrode. The plurality of partial recesses can leave a thickness of single crystal silicon between each of the partial recesses and the frontside of the silicon-based showerhead electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/871,586, filed Oct. 12, 2007, now U.S. Pat. No. 8,152,954, entitled“SHOWERHEAD ELECTRODE ASSEMBLIES AND PLASMA PROCESSING CHAMBERSINCORPORATING THE SAME.” This application is related to but does notclaim priority to U.S. application Ser. No. 12/409,984, filed Mar. 24,2009, entitled “ANCHORING INSERTS, ELECTRODE ASSEMBLIES, AND PLASMAPROCESSING CHAMBERS”; U.S. application Ser. No. 12/112,112, filed Apr.30, 2008, entitled “ELECTRODE ASSEMBLY AND PLASMA PROCESSING CHAMBERUTILIZING THERMALLY CONDUCTIVE GASKET AND O-RING”, and U.S. applicationSer. No. 12/050,195, filed Mar. 18, 2008, entitled “ELECTRODE ASSEMBLYAND PLASMA PROCESSING CHAMBER UTILIZING THERMALLY CONDUCTIVE GASKET”.

BACKGROUND

The present invention relates generally to plasma processing and, moreparticularly, to plasma processing chambers and electrode assembliesused therein. Plasma processing apparatuses can be used to processsubstrates by a variety of techniques including, but not limited to,etching, physical vapor deposition, chemical vapor deposition, ionimplantation, resist removal, etc. For example, and not by way oflimitation, one type of plasma processing chamber contains an upperelectrode, commonly referred to as a showerhead electrode, and a bottomelectrode. An electric field is established between the electrodes toexcite a process gas into the plasma state to process substrates in thereaction chamber.

BRIEF SUMMARY

According to one embodiment of the present invention, a silicon-basedshowerhead electrode is provided that can include a backside, afrontside, and a plurality of showerhead passages extending from thebackside of the silicon-based showerhead electrode to the frontside ofthe silicon-based showerhead electrode. The silicon-based showerheadelectrode can comprise single crystal silicon. The silicon-basedshowerhead electrode may further include a plurality of partial recessesformed within the single crystal silicon along the backside of thesilicon-based showerhead electrode. The plurality of partial recessescan leave a thickness of single crystal silicon between each of thepartial recesses and the frontside of the silicon-based showerheadelectrode.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent invention can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 is a schematic illustration of a plasma processing chamberincorporating particular aspects of some embodiments of the presentinvention;

FIG. 2 is a plan view of the backside of a showerhead electrodeaccording to one embodiment of the present invention;

FIG. 3 is a cross-sectional illustration of a portion of a showerheadelectrode according to one embodiment of the present invention;

FIG. 4 is an isometric illustration of the backside and thicknessdimensions of a showerhead electrode according to one embodiment of thepresent invention;

FIG. 5 is a cross sectional illustration of an electrode assemblyincluding securing hardware according to one embodiment of the presentinvention;

FIGS. 6, 7, 8A, and 9 are cross sectional illustrations of a portion ofan electrode assembly including securing hardware according to somealternative embodiments of the present invention;

FIGS. 8B and 8C are schematic illustrations presented to clarify thestructure and operation of the subject matter illustrated in FIG. 8A;and

FIGS. 10 and 11 illustrate securing hardware and complementary machinedportions of an electrode assembly according to a further alternativeembodiment of the present invention.

DETAILED DESCRIPTION

The various aspects of the present invention can be illustrated in thecontext of a plasma processing chamber 10, which is merely illustratedschematically in FIG. 1 to avoid limitation of the concepts of thepresent invention to particular plasma processing configurations, orcomponents, that may not be integral to the subject matter of thepresent invention. As is generally illustrated in FIG. 1, the plasmaprocessing chamber 10 comprises a vacuum source 20, a process gas supply30, a plasma power supply 40, a substrate support 50 including a lowerelectrode assembly 55, and an upper electrode assembly 100.

Referring to FIGS. 2-5, an upper electrode assembly 100 according to oneembodiment of the present invention is illustrated. Generally, theelectrode assembly 100 comprises securing hardware 60, alignment pins66, a thermal control plate 70, a silicon-based showerhead electrode 80,and a thermally conductive gasket 75 positioned between the frontside 74of the thermal control plate 70 and the backside 82 of the silicon-basedshowerhead electrode 80. More specifically, the thermal control plate 70comprises a backside 72, a frontside 74, and one or more process gaspassages 76 configured to direct process gas to the frontside 74 of thethermal control plate 70. Although the present invention is not limitedto particular thermal control plate materials or process gas passageconfigurations, it is noted that suitable thermal control platematerials include aluminum, aluminum alloys, or similar thermalconductors. In addition, it is noted that a variety of teachings may berelied upon in the design of thermal control plates including, but notlimited to, U.S. Pub. No. 2005/0133160.

The silicon-based showerhead electrode 80 comprises a backside 82, afrontside 84, and a plurality of showerhead passages 86 extending fromthe backside 82 of the silicon-based showerhead electrode 80 to thefrontside 84 of the silicon-based showerhead electrode 80. Thesilicon-based showerhead electrode 80 further comprises a plurality ofpartial recesses 88 formed in the backside 82 of the electrode 80. As isillustrated in FIG. 5, the partial recesses 88 leave a thickness x ofsilicon-based electrode material between the recess 88 and the frontside84 of the electrode 80. Backside inserts 90 are positioned in thepartial recesses along the backside 82 of the electrode 80. Thesilicon-based electrode material between the recess 88 and the frontside84 of the showerhead electrode 80 helps minimize potential source ofcontamination in the plasma processing chamber 10 by isolating thebackside inserts 90 and the securing hardware 60 from reactive speciesin the plasma chamber. To help ensure that the aforementioned isolationcan be maintained over the life of the electrode 80, the thickness x ispreferably at least approximately 0.25 cm or, stated differently, atleast approximately 25% of the total thickness of the silicon-basedshowerhead electrode 80.

Referring to FIG. 1, this isolation can be enhanced by configuring thethermal control plate 70 and the silicon-based showerhead electrode 80to define a hermetically sealed plasma partition 65 such that gas andreactive species within the evacuated portion 15 of the plasmaprocessing chamber 10 cannot reach the securing hardware 60 and theinserts. The particular manner in which the plasma partition 65 isdefined will vary depending on the respective configurations of thethermal control plate 70 and the showerhead electrode 80. It iscontemplated that in most cases, the respective materials forming thethermal control plate 70 and the showerhead electrode 80 will define themajority of the partition. In addition, it is contemplated that avariety of sealing members can be used to enhance the partition,particularly where the thermal control plate 70 and the showerheadelectrode 80 interface with each other and with other components of theplasma processing chamber 10.

Referring to FIG. 5, the aforementioned isolation of the backsideinserts 90 and the securing hardware 60 from reactive species in theplasma chamber 10 can be further enhanced by positioning the backsideinserts 90 in the partial recesses 88 such that they are inset or, atleast, flush relative to the backside 82 of the silicon-based showerheadelectrode 80. Similarly, the securing hardware 60 can be positioned insecuring hardware passages 78 in the thermal control plate 70 such thatit is inset or, at least, flush relative to a backside 72 of the thermalcontrol plate 70.

In addition to the process gas passages 76, the thermal control plate 70comprises securing hardware passages 78 that are configured to permitsecuring hardware 60 to access the backside inserts 90 positioned in thepartial recesses 88 along the backside 82 of the silicon-basedshowerhead electrode 80. The thermal control plate 70 and thesilicon-based showerhead electrode 80 can be engaged using the securinghardware 60 and the backside inserts 90. In the engaged state, thefrontside 74 of the thermal control plate 70 faces the backside 82 ofthe silicon-based showerhead electrode 80 and the showerhead passages 86in the silicon-based showerhead electrode 80 are aligned with theprocess gas passages 76 in the thermal control plate 70. In addition,the securing hardware passages 78 are aligned with the backside inserts90 positioned in the partial recesses 88 along the backside 82 of theelectrode 80. As a result, the securing hardware 60 may extend throughthe securing hardware passages 78 in the thermal control plate 70 andengage the backside inserts 90, which are positioned in the partialrecesses 88 along the backside 82 of the electrode 80.

The securing hardware 60 and the backside inserts 90 are configured tomaintain engagement of the thermal control plate 70 and thesilicon-based showerhead electrode 80. In addition, the securinghardware 60 and the backside inserts 90 are configured to permitdisengagement of the thermal control plate 80 and the showerheadelectrode 80. In the embodiment illustrated in FIG. 5, and otherembodiments described herein, the silicon-based electrode material ofthe silicon-based showerhead electrode 80 is isolated from frictionalcontact with the securing hardware 60 by the relatively resilientmaterial of the backside inserts 90 during engagement and disengagement.This isolation, provided by the backside inserts 90, serves to eliminateabrasion of the silicon-based electrode material by the securinghardware 60 as a source of contamination in the plasma chamber 10. Theresiliency of the backside inserts 90 also permit repeated,nondestructive engagement and disengagement of the thermal control plate70 and the silicon-based showerhead electrode 80.

Although a variety of materials may be selected to form the backsideinserts 90, including thermoplastics or other kinds of plastics,synthetic rubbers, ceramics, metals, or inserts with composite layers ofmaterials, according to some embodiments of the present invention, thebackside inserts comprise significant amounts of polyetheretherketone(PEEK) formulated and manufactured such that the hardness of thebackside inserts 90 does not exceed the hardness of the silicon-basedelectrode material. Additional candidate materials include, but are notlimited to Delrin® or other acetal resin engineering plastics formulatedas filled or unfilled homopolymers or copolymers, nylon,polytetrafluoroethylene (PTFE), or combinations thereof.

Although the thermal control plate 70 and the silicon-based showerheadelectrode 80 can be engaged in a variety of ways consistent with theconcepts of the present invention, in the embodiments illustrated inFIGS. 5, and 7-11, the backside inserts 90 can be configured as anchorsin the partial recesses 88 formed in the backside 82 of thesilicon-based showerhead electrode 80. More specifically, in theembodiment of FIG. 5, the backside insert 90 is anchored in the partialrecess by providing a threaded portion in the silicon-based electrodematerial. With the insert 90 in place, the securing hardware 60, whichmay for example comprise a threaded screw or bolt, engages the backsideinsert 90 to secure the showerhead electrode 80 to the thermal controlplate 70. In the embodiment of FIG. 7, the backside insert is anchoredin the partial recess via a bonding agent. In the embodiment illustratedin FIGS. 8A-8C, the partial recess 88 is machined to comprise anundercut portion 89 and the backside insert 90 is anchored in thepartial recess 88 by inserting the insert 90 into the recess 88 androtating it into the undercut portion 89 of the partial recess 88.

Referring to FIG. 9, it is noted that the backside insert 90 can beconfigured as a stud comprising a backside extension 92 that isconfigured to extend into one of the securing hardware passages 78 inthe thermal control plate 70. In which case, the securing hardware 60 isconfigured to access the backside extension 92 of the backside insert 90in the securing hardware passage 78 via, for example, a threadedengagement.

In any of the embodiments disclosed herein employing one or morebackside inserts 90, it will often be advantageous to ensure that thesecuring hardware 60, the backside inserts 90, and the partial recess 88are configured such that, during thermal loading, with the securinghardware 60 and backside insert 90 in an engaged state, the backsideinsert is able to move with the securing hardware within the partialrecess without dislodging from the recess. For example, referring to theembodiment of the present invention illustrated in FIGS. 10-11, where arefinement of the undercut embodiment illustrated above with referenceto FIGS. 8A-8C is illustrated, the backside insert 90 is provided withtabs 95 that are configured to complement the undercut portions 89formed in the electrode material of the showerhead electrode 80. Theinsert 90 can be secured in the recess 88 by aligning the tabs 95 withthe corresponding grooves 85 in the electrode 80, inserting the insert90 in the recess 88, and rotating the insert 90, as defined by thegrooves 85.

In the embodiment of FIGS. 10 and 11, the insert 90 can be secured inthe recess 88 in a spring-loaded state by providing a spring about areduced diameter portion 94 of the buried end 96 of the insert 90 andthe outside diametrical dimensions of the insert 90 and the size andshape of the tabs 95 are chosen to allow for movement of the insert 90in the partial recess 88 in the spring-loaded state. As a result, duringthe thermal loading typically present in plasma processing, the backsideinsert 90 can move with the securing hardware 60 within the partialrecess 88 without dislodging from the recess 88 and without degradingthe engagement of the securing hardware 60 and the insert 90.

The present inventors have recognized that any abrasive contact with theelectrode material in the vicinity of the recesses 88 can create asource of potential contamination in the plasma processing chamber 10.Accordingly, where a backside insert 90 according to the presentinvention is configured for installation or removal with a screwdriveror other potentially abrasive tool, as is the case in the embodiment ofFIGS. 10-11, it is contemplated that the slotted driving head of thebackside insert 90 can be provided with lateral shielding portions 98 atthe edges of the slot or other engaging portion with which the removaltool is to mate. Stated more generally, the backside insert 90 maycomprise one or more lateral shielding portions 98 configured to permita tool to engage the backside insert at a tool engaging portion thereofwithout extending beyond the periphery of the insert where it could comeinto contact with the inside diameter of the recess in the electrodematerial.

A variety of spring-loaded configurations can be utilized to reduce anytendency of the securing hardware 60 to become disengaged as a result ofstress induced as a result of thermal loading induced during plasmaprocessing. For example, one configuration for providing a spring-loadedengagement of the thermal control plate 70 and the silicon-basedshowerhead electrode 80 is illustrated in FIGS. 5-7. In FIGS. 5 and 7,the backside insert 90 is configured as an anchor in one of the partialrecesses 88 formed in the backside 82 of the showerhead electrode 80 andthe securing hardware 60 comprises a spring element in the form of aspring-loaded washer 62 configured to oppose a force of engagementprovided when the securing hardware 60 accesses the backside insert 90.In FIG. 6, the backside insert is omitted in favor of direct threadedengagement with a tapped hole in the electrode material. Alternatively,as is illustrated in FIG. 9, the spring element can be provided as ahelical spring 64 arranged about a longitudinal extension of thesecuring hardware 60 in the securing hardware passage 78.

Although the various concepts of the present invention have beendescribed herein in the context of silicon-based electrode materialssuch as single crystal silicon, polysilicon, silicon nitride, andsilicon carbide, it is noted that the present invention has utility in avariety of contexts, including those where the silicon-based electrodematerial comprises boron carbide, aluminum nitride, aluminum oxide, orcombinations thereof. In addition, it is contemplated that thesilicon-based showerhead electrode 80 may be presented in a variety ofconfigurations without departing from the scope of the present inventionincluding, but not limited to, a single-piece, circular showerheadconfigurations or multi-component, circular showerhead configurationscomprising a circular central electrode and one or more peripheralelectrodes arranged about the circumference of the central electrode.

It is noted that recitations herein of a component of the presentinvention being “configured” to embody a particular property or functionin a particular manner are structural recitations as opposed torecitations of intended use. More specifically, the references herein tothe manner in which a component is “configured” denotes an existingphysical condition of the component and, as such, is to be taken as adefinite recitation of the structural characteristics of the component.

It is noted that terms like “preferably,” “commonly,” and “typically,”when utilized herein, are not utilized to limit the scope of the claimedinvention or to imply that certain features are critical, essential, oreven important to the structure or function of the claimed invention.Rather, these terms are merely intended to identify particular aspectsof an embodiment of the present invention or to emphasize alternative oradditional features that may or may not be utilized in a particularembodiment of the present invention.

For the purposes of describing and defining the present invention it isnoted that the term “approximately” is utilized herein to represent theinherent degree of uncertainty that may be attributed to anyquantitative comparison, value, measurement, or other representation.The term is also utilized herein to represent the degree by which aquantitative representation may vary from a stated reference withoutresulting in a change in the basic function of the subject matter atissue.

Having described the invention in detail and by reference to specificembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of theinvention defined in the appended claims. More specifically, althoughsome aspects of the present invention are identified herein as preferredor particularly advantageous, it is contemplated that the presentinvention is not necessarily limited to these preferred aspects of theinvention.

It is noted that one or more of the following claims utilize the term“wherein” as a transitional phrase. For the purposes of defining thepresent invention, it is noted that this term is introduced in theclaims as an open-ended transitional phrase that is used to introduce arecitation of a series of characteristics of the structure and should beinterpreted in like manner as the open-ended preamble term “comprising.”

1. A silicon-based showerhead electrode comprising: a backside, afrontside, and a plurality of showerhead passages extending from thebackside of the silicon-based showerhead electrode to the frontside ofthe silicon-based showerhead electrode wherein the silicon-basedshowerhead electrode comprises single crystal silicon; and a pluralityof partial recesses formed within the single crystal silicon along thebackside of the silicon-based showerhead electrode, the plurality ofpartial recesses leaving a thickness of single crystal silicon betweeneach of the plurality of partial recesses and the frontside of thesilicon-based showerhead electrode.
 2. A silicon-based showerheadelectrode as claimed in claim 1 wherein the silicon-based showerheadelectrode further comprises a backside insert positioned in one of theplurality of partial recesses along the backside of the silicon-basedshowerhead electrode.
 3. A silicon-based showerhead electrode as claimedin claim 2 wherein the hardness of the backside insert does not exceedthe hardness of the single crystal silicon.
 4. A silicon-basedshowerhead electrode as claimed in claim 2 wherein the backside insertcomprises polyetheretherketone (PEEK) formulated and manufactured suchthat the hardness of the backside insert does not exceed the hardness ofthe single crystal silicon.
 5. A silicon-based showerhead electrode asclaimed in claim 2 wherein the backside insert is positioned in one ofthe plurality of partial recesses such that the backside insert is insetrelative to the backside of the silicon-based showerhead electrode.
 6. Asilicon-based showerhead electrode as claimed in claim 2 wherein thebackside insert comprise a tool engaging portion and one or more lateralshielding portions configured to permit a tool to engage the backsideinsert without extending beyond the periphery of the backside insert. 7.A silicon-based showerhead electrode as claimed in claim 2 wherein thebackside insert is an anchor in one of the plurality of partial recessesformed in the backside of the silicon-based showerhead electrode.
 8. Asilicon-based showerhead electrode as claimed in claim 7 wherein thebackside insert comprises tabs that complement undercut portions formedin the single crystal silicon in an insert and rotate manner.
 9. Asilicon-based showerhead electrode as claimed in claim 8 wherein thebackside insert is secured in one of the plurality of partial recessesin a spring-loaded state.
 10. A silicon-based showerhead electrode asclaimed in claim 9 wherein the outside diametrical dimensions of thebackside insert and the size and shape of the tabs allow for movement ofthe backside insert in one of the plurality of partial recesses in thespring-loaded state.
 11. A silicon-based showerhead electrode as claimedin claim 7 wherein the backside insert is anchored in one of theplurality of partial recesses by a threaded portion formed in the singlecrystal silicon.
 12. A silicon-based showerhead electrode as claimed inclaim 7 wherein one of the plurality of partial recesses comprises anundercut portion and the backside insert is anchored in one of theplurality of partial recesses such that the backside insert at leastpartially extends into the undercut portion of one of the plurality ofpartial recesses.
 13. A silicon-based showerhead electrode as claimed inclaim 7 wherein the backside insert is a stud comprising a backsideextension.
 14. A silicon-based showerhead electrode as claimed in claim1 wherein the thickness of the single crystal silicon between each ofthe plurality of partial recesses and the frontside of the silicon-basedshowerhead electrode is at least approximately 0.25 cm.
 15. Asilicon-based showerhead electrode as claimed in claim 1 wherein thethickness of the single crystal silicon between each of the plurality ofpartial recesses and the frontside of the silicon-based showerheadelectrode is at least approximately 25% of the total thickness of thesilicon-based showerhead electrode.
 16. A silicon-based showerheadelectrode as claimed in claim 1 wherein the silicon-based showerheadelectrode is a single-piece, circular showerhead.
 17. A silicon-basedshowerhead electrode as claimed in claim 1 wherein the silicon-basedshowerhead electrode is a multi-component, circular showerheadcomprising a circular central electrode and one or more peripheralelectrodes arranged about a circumference of the circular centralelectrode.